In the case of tiling, a tile is pressed onto a number of ridges of adhesive and the ridges are collapsed thereby forcing adhesive into the space between the ridges. During this process air which was within the space between the ridges should be expelled along the valleys and vented to the surrounding room or area. In this way the substrate should become covered with adhesive and likewise for the tile face pressed towards the substrate.
The process of tiling typically utilises a trowel with an edge characterised by regularly spaced rectilinear indentations. The interspacing, width and extent of the indentations depend upon the adhesive and tiles being worked. Further the indentations and interspacing typically have a castellated appearance. An example is illustrated in FIG. 4(a) of the accompanying drawings.
The prior known process of tiling has been found to be in practice not entirely satisfactory. It has been observed that under normal work practices some tiles may not be adequately adhered to a substrate surface and as a result the tiles may become loose or crack. Such a fault may not be found until after some months or years and may permit water to enter beneath the-tiles and lead to further problems. Consequently, often a loose or cracked tile can lead to a considerable problem which may be expensive to solve.
It is believed these problems may arise, at least partly, because in practice the substrate surface does not become uniformly covered with adhesive and as a consequence some parts of a tile are not adhered to the substrate. It is also believed that uppermost portions of adjacent ridges of adhesive spread out under the pressure of a tile being pressed to the substrate and contact and bridge the intervening space and may close the space between adjacent ridges of adhesive. Then the bridge of adhesive helps support the tile and resist the force pressing it into the adhesive and traps air underneath the tile.
As a result a void free of adhesive can be formed near the surface between adjacent ridges.
As will be appreciated, using a prior known trowel the adhesive is spread generally over and keyed into the substrate and then combed with the edge bearing the indentations thus forming ridges of adhesive. As the tile is pushed into place it is moved transverse to the ridges back and forth to collapse the ridges and expel the air from between the ridges of adhesive. With a large tile the surface area is significant and the required force to expel the air and collapse the ridges of adhesive is considerable and so proper setting of the tile may not be achieved.